Gas-operated self-loading firearm



Nov. 8, 1949 c. G. SWEBILIUS GAS-OPERATED SELF-LOADING FIREARM 2 Shts-Sheet 1 Filed Dec. 18, 1947 W m Md flff'ornega 6M gm m 3 mm M5 sin 3 Q1 I E o- Nov. 8, 1949 c. G. SWEBILIUS GAS-OPERATED SELF-LOADING FIREARM 2 Sheets-Sheet 2 Filed Dec. 18, 1947 Patented Nov. 8, 1949 UNITED. STATES OFFHCE 1 Claim. 1

The present invention relates in general to firearms and more especially to a self-loading firearm having improved gas-operated actionslide mechanism.

An object of the invention is to provide a superior gas-operated self-loading firearm.

A further object of the invention is to provide a self-loading firearm having superior gasoperated, action-slide mechanism wherein the elements thereof are symmetrically arranged in an economy of space so as to effect maximum efficiency, minimum wear, and smooth and uniform operation of the firearm.

With the above and other objects in view, as Will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a broken side elevation partly in section on the vertical longitudinal axis of a gasoperated self-loading firearm embodying the improved gas-operated action-slide mechanism of this invention, the action being in its closed position;

Fig. 2 is a broke side elevation partly in section of the firearm shown in Fig. 1, but with the action open;

Fig. 3 is a broken bottom plan view of the firearm shown in Fig. 1, but with the fore-end removed;

Fig. 4 is a section of the barrel, action-slide, yoke and fore-end assembly on line 4 -4 of Fig. l

Fig. 5 is a section on line 5-5 of Fig. 1 showing the tongue-portion of the fore-end nested in the flanged guard-plate on the forward end of the receiver;

Fig.6 is an exploded fragmentary perspective view of the action-slide block and the action-slide operating-mechanism; and

Fig. 7 is a perspective view of the action-spring guide-rod and the buffer for the action-slide operating-means.

Referring to Fig. 1, the particular firearm selected for the purpose of illustrating one embodiment of the invention is a self-loading gasoperated firearm comprising, in general, a receiver ID, a barrel ll secured to the forward end of the receiver, a buttstock I2 having a triggerplate I 3 mounted on the forward end thereof, the latter being arranged to be demountably secured on theunderside of the receiver and to provide an end-closure for the open rear end of the receiver, and gas-operated action-slide means indicated generally at M mounted on the underside of the barrel and adapted normally to be concealed by a wooden fore-end I5. The receiver ID and trigger-plate It may be viewed together as constituting a frame for the action and firecontrol mechanism of the firearm.

The action or breech-bolt i6 is mounted in the chamber 17 of the receiver for longitudinal movement to and from breech-closing position and is adapted to be automatically locked in the latter position by elevation of the upper edge of its rear end it into engagement with a stop-shoulder IS on the underside of the top wall of the receiver. The forward and rearward movements of the breech-block, including locking and unlocking of the latter in the chamber of the receiver, are accomplished by the action-slide means I 4 and more especially by a lost-motion linkage embodyin a pair of action-slides 20 supported in longitudinal guide-slots 2| in opposite sides respectively of the receiver for reciprocable move ment therein, the action-slides being pivotally connected at their rear ends to the breechblock by a transverse pin 22 engaged in a rocker-shaped cam-slot 23 formed in a tongue 24 depending substantially vertically from the underside of the breechblock adjacent the rear end thereof. The action-slides '20 extend forwardly from the chamber of the receiver through suitable guideapertures 25 in the front wall 26 of the receiver and on opposite sides respectively of the barrel, the forward ends of the action-slides 20 being fixedly secured to opposite sides respectively of an action slide block 21 hereinafter described.

Other details of the breechblock such as, for example, the spring-loaded firing-pin indicated generally at 28 and the extractor-claw 29, as well as the locking and unlocking operations of the breechblock by reciprocation of the pair of action-slides 20, are well known and characteristic features of firearms of this particular type and since they relate only generally to the invention, a more detailed description of these ancillary features is omitted, Similarly, a description of the fire-control mechanism indicated generally by the trigger 3H and hammer 3|, is unnecessary to a clear and full disclosure of the present invention and, hence, has been omitted. For a complete description of the fire-control mechanism for this type of firearm, reference may be had to my co-pendin application Serial No. 739,997 filed April 8, 1947.

The action-slide block 21 is a solid substantially-rectangular member supported beneath the barrel by the afore-mentioned action-slides 2B for longitudinal movement relative to the barrel, the forward ends of the slides 26 being fixedly secured on opposite sides respectively of the block, as described and illustrated more fully in my copenoling application Serial No. 746,971, filed May 9, 1947. Referring particularly to Figs. 4 and 6, the top side of the action-slide block El is provided with a longitudinal shallow recess 32 which intersects the opposite. ends respectively of the block and comprises a cylindrical surface of revolution concentric to the periphery of thebarrel, the recess 32 being symmetrical with respect to the longitudinal axis of the'latter and the axis of the action-slide block 27- so as torprovide clearance for the barrel and yet enable the block 21 to hug the undersidethereof;

The bottom of the slide-block is shown; provided with a longitudinal substantially-rectangular groove 33 which is symmetrical with respect to the longitudinal axis of the block and intersects the'opposite ends thereof, the width of the groove being substantially equal to the width of the'yoke-portion of the action-slide operatingmeans hereinafter described.

The aforementioned action-slide operatingmeans is indicated generally at 34 and comprises an. elongated hollow cylindrical connecting-rod 35 hereinafter referred to as a tubular conrod provided at its rear end with a yoke-portion 36 and at its forward end with a piston hereinafter described. The yoke-portion 36 is preferably formed integrally on the rear end of the tubular conrod, 'althoughit may be formed separately and secured thereto in any suitable manner, and comprises an elongated substantially-rectangular block approximately equal in length to the length of the tubular concord 35'. The bottom 37 of the yoke-portion or block 36 of the tubular conrod I constitutes a cylindrical surface of revolution which. is concentric with the underside of. the tubular conrod and in the present embodiment is of. slightly-larger radius so as to form a shoulder 38' at the intersection of the. forward end. of the block. 36 with the rear end of thetubular conrod. The. latter construction is preferred from the standpoint of good machinedesign and strength but it will. be clear that the bottom of theyoke and. the. underside. of. the tubular conrod may constitute a smooth. uninterrupted. cylindrical surfaceof revolution.

The yoke-portion or block..36 of the tubular conrod-is generally rectangular in cross section with. the exception of its aforementioned curvilinear bottom 31. Formed in the lower halfof the block 36 and concentric to its curvilinear bottom. 3'? is a longitudinal aperture 39 which intersects the rear end of the block 36 and extends forwardly therethrough to intersect the rear end of the tubular conrod 35, the diameter. of the longitudinal aperture 36 beingequal to the diameter ofthe bore 253 of the tubular conrod 35 so as to form a continuous chamber 39-40 of uniforminternal diameter for accommodating the action-return spring, as. hereinafter described. The opposite sides 4! of the yoke-portion or block 36 extend upwardly substantially vertically from the curvilinear bottom 31 of. the block to its substantially-flat top. 42 which is at right angles to its vertical sides 4|, the height of the sides 4.! being substantially twice the diameter of thetubular conrod 35 whereby thetop'42 of theyokeportion is elevated above the upper surface there-- of.. The forward end of the yoke-portion 36 thus 4, forms a substantially-square shoulder 43 with the rear end of the tubular conrod 35.

Milled or otherwise formed in the flat top 42 of the yoke-portion 36 is a substantially-rectangular recess 4 which extends laterally across the width of the top 42 and longitudinally thereof from a point adjacent the shoulder 43 rearwardly a distance equal to the length of the action-slide block 21. Further, the width of the yoke-portion 36 of the tubular conrod 35 is substantially equal to the width of the longitudinal groove 33 in the underside of the action-slide block 21 (see Fig. 4) as a consequence of which the recessed portion 44 of the yoke 36 is adapted to fit nicely into the groove 33 of the action-slide block H with the bottom of the recess 44 in engagement with the top wall of its groove 33 and the front and rear shoulders45and lb' respectively of the recess 44 fitting; snugly against the front and rear faces respectively of the action-slide block 21, as shown especially well in Fig. 1. When assembled thusly, the yoke 36 and action-slide block 2? are adapted to be fastenedtogether by a transverse pin. 41 which is driven through transverse axiallyaligned apertures ltland .49 respectively of the action-slide. block and yoke.

The forward end of the tubular conrod 35 is closed by the rear wall of a solid. piston 5| which is of slightly-reduced diameter and is-terminated at its forward extremity by a relativelynarrow annular flange or piston-head 52 arranged to make a-smooth gas-tight sliding fit in the piston-chamber ofthe. gas-cylinder.

Thegas-cylinder is indicated. generally at1'53 (see Figs. 1 and 2) and comprises a rearwardlyopening piston-chamber .54 whichcommunicates with the boreof the barrel by. a gas-passage 55.

Thelatter issubstantially perpendicular to-the longitudinal axis of the piston-chamber 54 and is formed-ma web-5.6 which joins-the-gas-cylinder its piston-chamber 54 -on the underside of the barrel substantially parallel to its longitudinal axis and in the; vertical plane thereof, asshown to advantage in Fig. 3. The upper end ofbthe gas-passage55 intersects. the=boreof. the, barrel substantially intermediatethe-opposite ends: of the barrel-sleeve while the lower end of the gas? passage 55 intersects the.piston.-chamber adjacent. the forward-blind end 58 thereof.

In the present embodiment, the gas-cylinder 53 embodies a rearwardly-extending axiallyaligned cylindrical-s1eever59 which is substantially-one and one-halt times aslong. as the gascylinder. and. is. formed. separately; thereof being joined thereto'at its forward end-by asolderedor welded joint. The bore of the sleeve 59:isequal in diameter touthe bore ofmthe' piston-chamber 54. and hence forms a. rear; extension. thereof, the over-all length of the resultant piston-chamber corresponding substantiallytothe travel of the breechblock in moving from breech-olosing to breech-open position and vice versa.

The action-slide operating-means 34 embodies resilient-means. forresisting rearward displacement thereof on discharge of the firearm and for thereafter returning the action-slide operating-means and breechblock. to their normal forward. positions, asshown. in Fig. 2. In the presentembodiment, the. aforesaid resilient-meanscomprises. a. coil-spring 60- adapted to-be sup.-

ported throughout a major portion of its length in the longitudinal chamber 39-40 of the actionslide operating-means 34, the forward end of the coil-spring 60, hereinafter referred to as an action-spring, being in engagement with an abutment which, in the present embodiment, constitutes the: rear wall 50 of the solid piston L In the normal position of the action-slide operating-means 34, a portion of the actionspring extends rearwardly beyond the rear end of the chamber 39--40 and is adapted to be supported by guide-means comprising a solid rod 6| which is supported, in turn, within the convolutions of the action-spring, the forward end of the rod 6| extending into the rear end of the action-spring chamber 3940.. The rear end of the guide-rod is adapted to seat in an aperture or socket 62 formed in the front wall 26 of the receiver immediately beneath the barrel. Secured on the guide-rod adjacent its rear end and concentric thereto, is a buffer-means 63 comprising a substantially-solid cylindrical-member of hard fiber orequivalent material (see Fig. 7), the forward face of which provides both a stop for the rearwardly-moving action-slide operating-means 34 and a seat for the rear extremity of the action-spring B0. The fore-end I5 of-the firearm is adapted to be supported on the underside of the barrel, forwardly of the front wall 26 of the receiver, so

the front wall of the receiver, to receive the spring-guide rod 6|. The guard-plate 64 is adapted thus to be mounted against the front wall of the receiver, with the front face of the guard-plate constituting a seat for the rear face of the cylindrical buffer 63. The force of the action-spring thrusting against the buffer, thus serves to hold the guard-plate in its assembled position on the firearm. The guard-plate is provided, moreover, with a peripheral flange 61 bent forwardly substantially perpendicular thereto.

Referring to Fig. 4, the fore-end I5 is provided with a longitudinal axial groove in its top side to accommodate the action-slide mechanism and its operating-means 34, the upper edges of the groove having longitudinal inwardly-projecting lips adapted to extend over the corresponding upper edges of the action-slide block and action-slides to fully enclose the latter. The rear end of the fore-end is provided with a peripheral tongue-portion 68 (see Figs. 1 and 2) adapted to engage tightly with the inner walls of the peripheral flange 61 of the guard-plate, as indicated in Fig. 5, so as to firmly support the rear end of the fore-end. The forward end of the latter is secured to the barrel by a transverse screw 69 extending through apertures in opposite sides of the fore-end and an axiallyaligned aperture 10 in the web of the barrelsleeve.

The operation of the firearm is like that of similar gas-operated self-loading firearms and it will suffice to state that when the firearm is discharged, the high-pressure gas which is developed in the chamber of the barrel and drives the projectile forwardly out of the forward end thereof, escapes in part through the gas-passageinto the forward end of the piston-chamber 54 andacts against the piston-head 52 to drive the latter rearwardly in the piston-chamber 54 and its cylindrical extension 59. As the piston moves rearwardly, its tubular conrod 35, including its yoke-portion 36 which connects the piston to the action-slide block 21, forces the latter and its pair of action-slides 20 rearwardly, thereby unlocking the .breechblock from the stopshoulder IQ of the receiver and moving the breechblock rearwardly to extract and eject the fired cartridge. During the rearward movement of the piston and action-slide assembly, the action-spring is compressed. It will be appreciated, of course, that the strength of the actionspring is nicely balanced with the gas pressures developed within the piston-chamber so that the breechblock may complete its rearward excursion in the receiver. In this connection, it will be noted that the distance between the front face of the buffer 63 and the rear end of the yoke-portion 31 of the action-slide operating-means (when the latter is in its normal forward position) is substantially equal to the distance traveled by the breechblock in moving rearwardly from its closed position to breech-open position. The :breechblock is adapted thus to be positively stopped at the end of its rearward excursion by engagement of the rear end of the yoke with the front face of the buffer, so as to prevent the rear end of the breechblock from striking the end-closure of the receiver.

As soon as the gas pressures diminish in the piston-chamber below the force of the compressed action-spring 60, the latter thereupon moves the piston action-slide assembly and breechbloek forwardly into their respective normal positions, the forward movement of the breechblock being accompanied by the feeding of a fresh cartridge from the box-magazine of the firearm into the chamber of the barrel. At the end of its forward movement, the rear end of the breechblock is elevated into locking engagement with the stop-shoulder l9 of the receiver, and the firearm is ready to discharge the next cartridge.

From the foregoing description it will be clear that the action-slide operating-means 34 and gas cylinder 53 are mounted on the underside of the barrel parallel to the longitudinal axis thereof and that by providing the piston of the pistonchamber 54 with a tubular conrod 35 having a yoke-portion at its rear end adapted to connect the piston the action-slide block 21, the actionspring of the firearm is adapted to be supported within the tubular conrod in axial alignment with the piston and substantially parallel to the longitudinal axis of the barrel. In accordance with this construction, the force of the spring so acting to resist the rearward movement of the piston and action-slide assembly, acts in axial alignment with the pressure exerted on the piston-head by the gases of explosion, whereby the maximum strength of the action-spring is utilized, as a consequence of which a relatively-small spring may be used, resulting in a more compact and neater design. Moreover, by reason of the symmetrical arrangement of the action-slide operating-means 34 (including its action-spring 60) and the action-slide block 21 and its pair of actionslides 20, the forces which drive the breechblock rearwardly in the receiver and return the breechblock to breech-closing position, are evenly divided on opposite sides respectively of the breechblock and act in the longitudinal direction of its movement; xthusxeliminatin'g. any *unlcialancediforce moments-which heretoforezhave been. the source 015-. lateral thrusts;andihenceexcessive friction-and we'arronr. these: sliding; elements; of: the: firearm;

The: invention. .mayv be. carried: out :in' other specific: ways" than; thoselherein set-v forthflwithout departing from the spirit-and essential: characteriStiCS.Of;.thB.. invention;- and the present embodimentstare; therefore-to: be considered. in: all respects asillustrative andinot restrictive; andiiall changes coming: within: the meaning and: equivalency-mange of? the appended.:claim arehint'ended tolbe embraced therein.

Asigasr-operated self-loading firearm, including inrcombinationn: a. receiver; a breechblock move ably m'ountedi in said receiver; a barrellprojecting forwardly-1from said receiver; a gas-cylinde'r onthe' underside of: said barrelihaving' aw rearwardlyopening piston-chamber communicatingrwiththe bore oft said barrel; actioneslide means comprising a slide blockrreciprocably mounted-on th'e under side or said-:barrel', :saidxslide-blockhavingza groove in the underside thereof: "and; a pair of spaced parallel action-ebarsextending rearwardly. from said "slide-block on-v opposite. sides respectively '.of saidv barreli: said action-bars being connectedrat theinrear. ends'to saidi breechblock; and operatin g-meansfor saidraction-slide means compris ing a rearwardly-openingstubular-conrod mount.-. ediionthe underside-f: said barrel substantially parallel; thereto. and: inr the vertical plane of said slide-block, said conrod having. a solidi piston: at: its: forward 'end'recipro'ca'bly engagedv in the said rearwardly-openingpiston-chamber, a yokev at therear endi ofusaid tubular conrod said -yoke 8; beingl-arnan'ged to :fitf snugly in thelgrooveof; said! slide-block: to .couple saidrconrodx thereto for. movement: in: a planeusubstantially' parallel: to; the longitudinaliiaxiaof saidibanrel and coincident: withlqthe verticali plane;-ofz;said slide-block but below' its: longitudina1 axis, fastening. meanaar ranged tosecuresaid slide-blocki andyoketo get'hen: in: coupled relationship, a coil-spring housed throughout-a major portionofa its-length in; the. rearwardly opening tubular. -.conrod, the forward endnofa said spring beingarrangedto. abut the rear wall of; said; solid piston, a springr-guide comprising :a: rod. supported .axiallywithin said coir-spring and arranged to engage=at :its. forward end;in.-the open rears end ofaisaid tubular-conrod andtoiseat at itsreanend in a: socket; in the front" Wall of said receiver; andajabufier-member com-- prising a substantially-solid ;hard:-fiber,-cylinder mounted-on said; guide-rod, the rear end of said: buffer-member being:- arranged to engage against the front Wall "of said. receiver and the forwardend of saidl-zbufferemember constituting a, fixed abutment 'bothfonthe rear. endiof said coilispring andsaidiyokez CARL- G; SWEBILIUSL:

REFERENCES CITED.

The following references are of record inthe file of this patent:

UNITED, STATES PA I-E NiI s, 

